Folding display frames are commonly used for assembling temporary upright display stands for holding display panels with graphic materials displayed at trade shows. Photomural displays and other graphics, projection screens, and product display shelves, for example, are commonly mounted on the portable display stands.
Folding display frames typically comprise a number of rigid frame members pivotally connected together at their ends in a collapsible and portable form. The framework in its expanded or open state commonly consists of a grid of horizontal and vertical rod members forming an array of cubicles. The frame is carried to the exhibition hall in its collapsed form and then is erected to form the rigid structural framework for a display stand. Display panels, which are mounted to the display frame, and other structural members of the supporting frame also are carried to the trade show in a compact form. The entire folding display system is then assembled into the finished display unit.
In a typical three-dimensional framework, a plurality of rod members are pivotally connected together to permit collapsing of the framework into a compact form in which the rod members lie substantially parallel to each other. Except where the framework is assembled in a substantially permanent structure, the rod members are pivotally joined at their ends to hubs at the corners of the cubicles so that the rods can be rotated relative to each other as the framework is adjusted between its open expanded configuration and its closed compact configuration.
One of the objectives in designing folding display frames is to make the structure light in weight and compact in its folded form to enhance ease of transportation and storage when the framework is not in use. At the same time, the framework, when fully expanded into its useful configuration, must be strong and fairly rigid. The framework must not only be strong enough to give adequate support, but it must also withstand abuse, particularly when being folded and erected. A commonly desirable display frame configuration is one in which the upright frame has a curved configuration, i.e., the frame is arcuate in the plan view shape of the expanded frame. Such an expanded frame configuration tends to be more stable than an expanded display frame in a flat form. However, the curved display frame also can be unstable because of its relatively large size and the relative light weight of the expanded frame. Because of the curved shape of the frame and because weight hung from the frame is always on the front side, the forces resisting forward tipping of the frame are concentrated on the front extreme left and right bottom hubs of the framework. This load causes a distortion of the bottom outer cubicles of the frame into parallelograms, with the outermost frame cubicle on either the left or right side moving upward with respect to the next inward vertical cubicle.
Thus, there is a need to provide a means for stabilizing such a display frame in its expanded form to prevent the display frame from tipping over under the weight normally carried by the frame during use.
Various stabilizing means can be used to either resist distortion of the expanded display frame, or to otherwise add to its stability. However, these stabilizing systems often have many disadvantages. For instance, addition of external stabilizing members can be a disadvantage if they unnecessarily add to the weight of the unit, or if they unreasonably increase the weight of the display system. Some stabilizing systems are unreasonably complex. One folding display frame uses four crossed diagonal braces within each frame array to provide stabilization. The stabilizing frame members of some display frames must be latched in place when the frame is expanded and then disconnected when the frame is folded. Aside from the additional time required to assemble the frame and then disassemble it, these devices also can be difficult to unlatch if the diagonal braces cannot easily move lengthwise. In other instances where stabilizing members are incorporated into the frame, the additional stabilizing members can prevent the frame from being collapsed into a compact folded position.
Thus, there is a need for a simple, lightweight folding display frame which can be quickly and easily unfolded and assembled into a stabilized expanded configuration. It is desirable for the framework to expand into its assembled stable form without the necessity of adding external stabilizing members once the frame is unfolded. The stabilized expanded display frame also should be foldable easily into a compact form without the stabilizing members unnecessarily increasing the folded size of the framework.